GATE Environmental Engineering Global and Regional Environmental Issues Syllabus

Global and Regional Environmental Issues syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Global and Regional Environmental Issues in GATE Environmental Engineering, not a summary of it.

1. 1

   Global effects of air pollution

   6 topics

   • Greenhouse gases
   • Global warming
   • Climate change
   • Urban heat islands
   • Acid rain
   • Ozone hole
2. 2

   Ecology and various ecosystems

   4 topics

   • Biodiversity
   • Factors influencing increase in population
   • Energy consumption
   • Environmental degradation

Global and Regional Environmental Issues flashcards for GATE Environmental Engineering

18 of 50 cards from the Global and Regional Environmental Issues deck — real questions with worked answers.

1. What are greenhouse gases (GHGs)?

   Atmospheric gases that absorb and re-emit infrared (long-wave) radiation, trapping heat in the lower atmosphere and causing the greenhouse effect. Major examples: $\ce{CO2}$, $\ce{CH4}$, $\ce{N2O}$, water vapour, $\ce{O3}$, and CFCs.

2. List the major anthropogenic greenhouse gases in decreasing order of their typical contribution to enhanced warming.

   Carbon dioxide ($\ce{CO2}$) > Methane ($\ce{CH4}$) > Nitrous oxide ($\ce{N2O}$) > Halocarbons/CFCs. Water vapour is the most abundant natural GHG but is largely a feedback, not a direct anthropogenic emission.

3. Define Global Warming Potential (GWP).

   GWP is the ratio of the heat (radiative forcing) trapped by a unit mass of a gas to that trapped by the same mass of $\ce{CO2}$ over a chosen time horizon (usually 100 years). By definition $\text{GWP}_{\ce{CO2}} = 1$.

4. Give approximate 100-year GWP values for $\ce{CH4}$ and $\ce{N2O}$ relative to $\ce{CO2}$.

   Methane $\ce{CH4} \approx 25$ (newer estimates $\approx 28\text{--}34$); Nitrous oxide $\ce{N2O} \approx 298$. Reference $\ce{CO2} = 1$.

5. What is the greenhouse effect?

   Incoming short-wave solar radiation passes through the atmosphere and warms the Earth's surface, which re-emits long-wave infrared radiation. GHGs absorb this outgoing IR and re-radiate it back, keeping the surface warmer (about $\ce{+33}\,^{\circ}\text{C}$ warmer, i.e. $\approx 15\,^{\circ}\text{C}$ instead of $-18\,^{\circ}\text{C}$).

6. What is radiative forcing?

   The change in net radiative flux (downward minus upward, in $\text{W/m}^2$) at the tropopause caused by a perturbation such as increased GHG concentration. Positive forcing warms the climate system; negative forcing cools it.

7. Distinguish 'global warming' from 'climate change'.

   Global warming is the long-term rise in Earth's average surface temperature due to GHG accumulation. Climate change is the broader, long-term alteration of climate patterns (temperature, precipitation, winds, extreme events) of which global warming is one component.

8. What is the main natural greenhouse gas, and why is it usually not regulated?

   Water vapour ($\ce{H2O}$) is the most abundant GHG. It is not directly regulated because its concentration is controlled by temperature (a feedback) and has a very short atmospheric residence time of days, rather than being a long-lived emitted pollutant.

9. State the principal anthropogenic source of atmospheric $\ce{CO2}$.

   Combustion of fossil fuels (coal, oil, natural gas), followed by deforestation and cement (limestone calcination) production: $\ce{CaCO3 -> CaO + CO2}$.

10. What is the approximate pre-industrial vs current atmospheric $\ce{CO2}$ concentration?

    Pre-industrial $\approx 280\ \text{ppm}$; current $> 415\ \text{ppm}$ (and rising by roughly $2\ \text{ppm/yr}$).

11. Define carbon dioxide equivalent ($\ce{CO2}$-eq).

    A common metric expressing the warming effect of a mix of GHGs as the mass of $\ce{CO2}$ that would produce the same radiative forcing: $$\text{CO2eq} = \sum_i (m_i \times \text{GWP}_i)$$ where $m_i$ is the mass of gas $i$.

12. What is an Urban Heat Island (UHI)?

    A metropolitan area that is significantly warmer than its surrounding rural areas, due to human activities and built surfaces. The UHI intensity is the temperature difference $\Delta T_{u-r} = T_{urban} - T_{rural}$.

13. List the main causes of the Urban Heat Island effect.

    Low-albedo surfaces (asphalt, concrete) absorbing solar heat; reduced vegetation/evapotranspiration; waste/anthropogenic heat from vehicles, AC and industry; urban canyon geometry trapping radiation; reduced wind flow; impervious surfaces reducing evaporative cooling.

14. Name common mitigation measures for Urban Heat Islands.

    Increasing green cover and urban forests; cool/reflective (high-albedo) roofs and pavements; green roofs; water bodies and fountains; permeable surfaces; better urban ventilation and reduced waste heat.

15. Define albedo.

    Albedo is the fraction of incident solar radiation reflected by a surface: $$\alpha = \frac{\text{reflected radiation}}{\text{incident radiation}}$$ ranging from $0$ (perfect absorber) to $1$ (perfect reflector). Fresh snow $\approx 0.8$; asphalt $\approx 0.1$.

16. What is acid rain and what pH defines it?

    Acid rain is precipitation with pH below the natural value of $\approx 5.6$ (often $< 5.0$), caused by atmospheric $\ce{SO2}$ and $\ce{NO_x}$ forming sulfuric and nitric acids. Natural rain is mildly acidic due to dissolved $\ce{CO2}$ forming $\ce{H2CO3}$.

17. Why is unpolluted rainwater naturally acidic at pH $\approx 5.6$?

    Atmospheric $\ce{CO2}$ dissolves in water forming weak carbonic acid: $$\ce{CO2 + H2O <=> H2CO3 <=> H+ + HCO3-}$$ giving a baseline pH of about $5.6$.

18. Write the chemical reactions forming sulfuric acid in acid rain.

    $$\ce{2SO2 + O2 -> 2SO3}$$ $$\ce{SO3 + H2O -> H2SO4}$$ (Also directly: $\ce{SO2 + H2O -> H2SO3}$ forming sulfurous acid.)

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